effects of citrus rootstocks on fruit yield and quality of...

Nadori E.B. et al. (2020). AFRIMED AJ –Al Awamia (129). p. 211-225

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Effects of Citrus Rootstocks on Fruit Yield and Quality of ‘Nadorcott’ Mandarin

Nadori E.B.1, El Guilli M.2, Hamza A.2, Samdi A.2, Baiz. Z.2 and Kharbouch E.3

[email protected]

1: Research and citrus grower (Sebnakh sarl farm.), North-West of Morocco.

2: Research scientist in National Institute of Agronomic Research (INRA), Kenitra, Morocco.

3: Technician at Sebnak farm, North-West of Morocco.


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Abstract The effects of citrus rootstocks on the performance and fruits characteristics of

commercial varieties are known and well documented. These effects, as well as the

resistance to biotic and abiotic stresses, constitute the main criteria that direct the

rootstock choice for a new citrus orchard. The Moroccan variety ‘Nadorcott’ mandarin

also called ‘W. Murcott’ and ‘Afourer’ is relatively new. ‘Nadorcott’ is a popular late

mandarin cultivar, owing to its good eating quality and excellent bearing capacity.

Thus, there are few undertaken research and available results related to its behavior

on the widely used rootstocks in the main citrus growing areas of Morocco Kingdom.

This paper presents the results of a field trial carried out in the North West Morocco,

a coastal area, to evaluate the effects of five rootstocks on ‘Nadorcott’ yield and fruit

quality: juice content, total soluble solids (TSS), acid content (A), maturity index

expressed as TSS/A ratio and Citrus Color Index (CCI). The results show that the

highest yields were observed on citrange C-35 and Citrus macrophylla (MAC) over

the three seasons. Additionally, percentage of juice content over two successive

years of fruits produced on C-35, Troyer citrange (CT), Carrizo citrange (CC) and

Swingle citrumelo (SW) was about 53 % but did not exceed 50 % for Citrus

macrophylla. The highest TSS was obtained on CC rootstock. However, the TSS was

less than 10 in 2013 and around 11 °Brix in 2014 for Citrus macrophylla and above

12 °Brix for the other rootstocks. Regarding the maturity index, apart from the low

value (11.3) scored by MAC, in 2013 due to a low TSS, there was no significant

difference between the maturity indices of the fruits of the mandarin 'Nadorcott'

produced on the different rootstocks tested. Furthermore, the five rootstocks had no

effect on the fruit color parameters of 'Nadorcott' mandarin.

Keywords: citrus, Nadorcott, rootstock, yield, quality.


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Effets du porte-greffe sur le rendement et la qualité des fruits de la mandarine «Nadorcott»

Résumé Les effets des porte-greffes d'agrumes sur les performances et les caractéristiques des fruits des variétés commerciales sont connus et bien documentés. Ces effets, ainsi que la résistance aux stress biotiques et abiotiques, constituent les principaux critères qui orientent le choix d’un porte-greffe pour la mise en place d’un nouveau verger d'agrumes. La variété marocaine de mandarine «Nadorcott» également appelée «W. Murcott » ou « Afourer » un mandarinier tardif populaire, en raison de sa bonne qualité gustative et de son excellente capacité productive. Peu de recherche ont été entreprises et peu de résultats sont disponibles sur son comportement en association avec les porte-greffes largement utilisés dans les principales zones de production d'agrumes au Maroc. Cet article, présente les résultats d'un essai porte-greffe installé dans le nord-ouest du Maroc, une zone côtière, dans le but d’évaluer les effets de cinq porte-greffes sur le rendement de la 'Nadorcott' et sur la qualité des fruits notamment la teneur en jus, les sucres solubles totaux (TSS), l’acidité (A), l’indice de maturité exprimé par le rapport (TSS/A) et sur la coloration de l’écorce exprimée par Citrus Color Index (CCI). Les résultats obtenus montrent que les rendements les plus élevés, au cours des trois saisons, ont été réalisés par le citrange C-35 et le Citrus macrophylla (MAC). En outre, le pourcentage de teneur en jus, sur deux années consécutives, des fruits produits avec le C-35, le citrange ‘Troyer’ (CT), le citrange ‘Carrizo’ (CC) et le citrumelo ‘Swingle’ (SW) était d'environ 53% mais il ne dépassait pas 50 % pour le Citrus macrophylla. Le TSS le plus élevé a été obtenu avec le porte-greffe CC. Cependant, le TSS était inférieur à 10 en 2013 et autour de 11 °Brix en 2014 pour le Citrus macrophylla et il était supérieur à 12 °Brix pour les autres porte-greffes. Concernant l'indice de maturité, hormis la valeur de (11,3) notée par MAC, en 2013 en raison d'un TSS faible, il n'y avait pas de différence significative entre les indices de maturité des fruits du mandarin 'Nadorcott' produits sur les différents porte-greffes testés. De plus, les cinq porte-greffes n'ont eu aucun effet sur les paramètres de couleur des fruits du mandarinier 'Nadorcott'.

Mots clés: agrumes, Nadorcott, porte-greffe, rendement, qualité.


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ة وعلى جودةتأثير حوامل طعم الحمضيات على اإلنتاجي

’نادوركوت‘ فاكهة ماندرين

النا ضوري ا.ب1؛ الڭيلي م.2؛ حمزة ع.2؛ الصمدي ع. 2 ؛ ابعيز ز. 2 ؛ خربوش ا. 3

ملخص

وفة وموثقة جيدًا. إن تأثيرات حوامل طعم الحمضيات على أداء وخصائص ثمار األصناف التجارية معر

يوية وغير الحيوية، تشكل المعايير الرئيسية التي توجه ، باإلضافة إلى مقاومة الضغوط الحهذه التأثيرات

ايضا ’نادوركوت‘الجديد نسبيًا اختيار حامل الطعم لبستان حمضيات جديد. يُطلق على الصنف المغربي

هو أحد أصناف الماندرين المتأخرة، له جودة وقدرة ’نادوركوت‘. ’M. Murcott‘أو ’Afourer‘اسم

قليل من األبحاث التي تم إجراؤها على سلوك النادوركوت مع حوامل الطعم إنتاجية عالية. هناك عدد

المستخدمة في مناطق زراعة الحمضيات الرئيسية في المملكة المغربية. في هذا البحث نقدم، نتائج

تجربة أجريت في شمال غرب المغرب، وهي منطقة ساحلية، لتقييم آثار خمسة حوامل طعم على

،(TSS)السكر ، ((Aودة الفاكهة: محتوى العصير، المحتوى الحمضي وج ’نادوركوت‘محصول

أظهرت النتائج أن أعلى . (CCI) تومؤشر لون الحمضيا (TSS/A) مؤشر النضج المعبر عنه بنسبة

خالل الفصول الثالثة. citrange C-35 و Citrus macrophylla إنتاجية قد لوحظت على

وية لمحتوى العصير على مدى سنتين متتاليتين من الفاكهة المنتجة باإلضافة إلى ذلك، كانت النسبة المئ

Citrusبالنسبة ل ٪50ولكنها لم تتجاوز ٪53حوالي Swingle وC-35, CT, CC على

Macrophylla تم الحصول على أعلى نسبة . TSS فيCC .أقل من ت نسبة السكر ومع ذلك، كان

12وأكثر من Citrus Macrophylla في 2014درجة بريكس في 11وحوالي 2013في 10

درجة بريكس عند حوامل الطعم األخرى. فيما يتعلق بمؤشر النضج، بصرف النظر عن القيمة

و بسبب انخفاض نسبة السكر، 2013، في Citrus Macrophylla( التي سجلتها 11.3المنخفضة )

على حوامل طعم مختلفة. عالوة ’تنادوركو‘لم يكن هناك فرق كبير بين مؤشرات نضج ثمار ماندرين

.’نادوركوت‘ين ر( لثمار ماند(CCIعلى ذلك، لم يكن لحوامل الطعم الخمسة أي تأثير على لون الفاكهة

الجودة. المحصول،، حامل الطعم، نادوركوت الحمضيات، :المفتاحيةالكلمات


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Introduction

Citrus grower’s income depends mainly on the yield and quality of the fruit. Their ability to achieve high profits, is however, largely a matter of the orchard management system and the right choices made at the start of the orchard site and the rootstock. Indeed, rootstocks are very important for adaptability to pedo-climatic conditions as well as for tolerance to major biotic and abiotic stresses. In addition to their effect on the earliness and the quality of the fruits (Castle, 1995). In Morocco, as is the case in many citrus-growing countries, the use of sour orange as a rootstock rapidly declined due to the threat of tristeza virus. Researchers and citrus growers have mobilized their efforts to find alternative rootstocks. The mandarin variety ‘Nadorcott’ (Citrus reticulata Blanco), also known under the names ‘Afourer’ in Morocco and the European Union, ‘W. Murcott’ and ‘Delite’ in the United States of America, is a Moroccan hybrid selection of ‘Murcott’ and an unknown pollinator parent (Nadori, 1998, 2004). It is reported as self-incompatible and produces seedless fruit in the absence of cross-pollination (Bono and al., 2000; Chao, 2005).The flesh of fruit is very juicy and sweet, with high sugar content and good acidity level. Fruit reaches commercial maturity in mid to late February (Agusti, 2014). Being a new variety of a great commercial prospect, few studies have been reported about its behavior on different rootstocks. The objective of this study is to evaluate the effect of five rootstocks on ‘Nadorcott’ trees productivity and on fruit quality.


216

Materials and Methods

Field trial and plant material

In this field trial, Nadorcott’ mandarin was budded onto the following five rootstocks (treatments): ‘Troyer’ citrange [(Citrus sinensis (L.) Osbeck × Ponicrus trifoliate (L.) Raf. ] (CT), ‘Carrizo’ citrange [(Citrus sinensis (L.) Osbeck × Ponicrus trifoliate (L.) Raf. ] (CC), ‘Swingle’ citrumelo [P. trifoliata (L.) Raf. × Citrus paradisi Macfad.)] (SW), C-35 citrange (C35) and Citrus macrophylla (M). This experimental grove was planted in June 2008 at Caidat of Bahhara Oulad Ayad, province of Kenitra, Gharb region. In SEBNAK farm located 2 km from Atlantic coast, in North-West of the Morocco kingdom (Latitude: 34°46’41.5’’N, Longitude: 6° 19’59.5’’W). The weather in the farm zone is quite humid compared to the other Moroccan citrus areas: year rainfall varies strongly (400 to 800 mm), high temperatures in summer, moderate sunlight during late autumn and winter with low temperatures that can drop to -5 °C in December, January or February. In this period, fog, mist and dew are frequent and reduce harvest time to few hours per day. The land is waving and the soil is well drained. Its texture is sandy to loamy in the 0-30 cm horizon layer and loamy with porous rocks and red clay in lower strata. There is no lime and pH is neutral (7 to 7.5). Drip irrigation is realized by pumped underground water, which is of good quality. Adopted spacing for planting is 6 m x 2 m. (HCP, 3013).

Yield and Fruit quality measurements

Fruits were harvested and weighed per tree during the harvest seasons of the years 2013 to 2015. Monitored quality parameters are: Juice content: as ratio (%) of the weight of the fruit juice and that of fresh fruit. The

juice is extracted by pressing 20 fruits in an electric press juice on a rotating rotor. Titratable acidity (TA): citric acid quantity per 100 g of juice as determined by

proportioning a sodium hydroxide solution 0.1N with endpoint pH 8.1. Phenolphthalein (1%) was used as a color indicator (AOAC, 2011).

Total soluble solids (TSS) as sugars or °Brix determined using a digital hand-held

refractometer.


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Fruit color measurements

Fruit skin color was randomly measured on two opposite sites at fruit equator usinga Konica Minolta CR-400 Chroma Meter (Minolta CR-400, Japan). The Hunter Lab parameters (L, a and b) were used to calculate the corresponding Citrus Color Index (CCI) using the following equation: CCI = (1000 * a) / L * b; where ‘L’ represents the relative lightness of color with ‘a’ range from 0 (darkness) to 100 (brightness). Both ‘a’ and ‘b’ scales are varying from -60 to 60. ‘a’ value represents greenish and redness as the value increase from negative to positive, while ‘b’ is negative for blueness and positive for yellowness.

Statistical analysis

The trial was installed according to a complete randomized block design with five replicates and five trees per plot. Data were collected and analyzed using SAS system and the means compared by T test (LSD) at the ≤ 0.05 % level of probability.


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Results and discussion

Fruit yield

The results of the effects of different rootstocks on fruit yield of ‘Nadorcott’ mandarin are shown in Fig.1. The highest cumulative yields of ‘Nadorcott’ mandarin, during the three considered seasons, were obtained from the trees on C-35 citrange and on Macrophylla with cumulative yields of around 154 and 142 t/ha respectively. The trees on Carrizo citrange had the lowest cumulative yield (124 t/h). The trees on Troyer citrange and Swingle citrumelo produced similar yield and did not show any significant difference. In general, vigorous rootstocks like Macrophylla would induce high fruit yield (Al-Jaleel and Zekri, 2003). Similarly, in Brazil significant effects of rootstocks on fruit yield of Satsuma mandarin were also detected (Cantuarias-Avilés and al., 2010).

We note that for the five rootstocks, there is inter-annual variability in productivity (Fig. 1). This alternate bearing phenomena was reported by other researchers (Stander and al., 2017; Stander and Cronjè, 2016). The alternating yields of 'Nadorcott' mandarin can be explained by the fact that ‘Nadorcott’ is a late maturing mandarin cultivar that developed from a seedling of the strongly alternate-bearing ‘Murcott’ mandarin (Nadori, 2006) and can be prone to alternate bearing under certain hormonal or/and nutritional conditions (Stander and al., 2017; Stander and Cronjè, 2016).

The hormonal theory of alternate bearing suggests that phytohormones are responsible for floral inhibition during an ‘‘on’’ year (Martínez-Alcàntara and al., 2015; Muñoz-Fambuena and al., 2011; Verreynne and Lovatt, 2009). The nutritional theory of alternate bearing, on the other hand, suggests that flowering response is determined by fruit load and availability of carbohydrates (Monerri and al., 2011; Dovis and al., 2014; Martínez-Alcàntara and al., 2015).

0

10

20

30

40

50

60

70

80

MAC C35 CC CT SW

Yie

ld (

t/h

a)

Rootstocks

MAC: Citrus macrophylla C35: C-35 citrange CC: Carrizo citrange CT: Troyer citrange SW: Swingle citrumelo

Fig.1: Average yield of "Nadorcott" mandarin grafted onto different rootstocks

2013

2014

2015

Yield difference among rootstocks and their interactions with different citrus cultivars could be attributed to differences in morphology and physiology of rootstocks, which are reflected as tree growth vigour, size and depth of roots, water and nutrients


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uptake capability, carbohydrate synthesis, and also their adaptation to climatic and soil conditions, good compatibility between rootstock and cultivar and the possibility of fruiting potential of a cultivar on certain rootstocks (Continella and al., 1998; Zekri and Parsons, 1989; Castle, 2010a). In Morocco, at El Menzeh experimental station, a behavioral study of three clementine clones 'Sidi Aissa', 'Ain Taoujdate' and 'Cadoux' on six common rootstocks, showed a graft incompatibility between these clones and trifoliate orange, and Marrakech citrange in other part. Production and development of trees were poor on both rootstocks. On the other four rootstocks, the clementine selections 'Sidi Aissa' and 'Ain Taoujdate' proved to be significantly more productive than 'Cadoux' which was the most multiplied in Morocco after the 1960 (Nadori and al., 1983a).

In three rootstocks trials, Nadori and al. (1983b) showed significant effects of these rootstocks on the productivity and quality of the fruits of the ‘Valencia late' orange, ‘Shambar’ grapefruit and clementine over a period of ten years. The 'Rangpur' and 'Rough lemon' gave the highest yields of fruit but with low quality, followed by the ‘Troyer citrange’ which gave the best internal quality. The mandarin 'Cleopatra' and ‘Sour orange’ have resulted in average yields and good quality fruit. The results were obtained on sandy, non-calcareous soil at neutral pH.

Juice content

With regard to the juice content, the CC, CT, SW and C-35 rootstocks ensured a high percentage of juice, contrariwise MAC recorded a slightly lower rate (Fig. 2 and 3). However, fast and important decrease of fruit quality, mainly percentage of juice and acidity, were observed during cold storage on fruit harvested from trees on Macrophylla. These fruits can’t be marketed forty days after harvest even under cold storage (El Guilli and al., 2016). Castle and al. (1993) reported that trees on Macrophylla in rootstock trials have consistently produced fruit with the lowest juice quality. For all rootstocks, the fruit juice content meets the standards for export of the fruits of Moroccan mandarin that must be at least 40 %.

bab

a abab

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25

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35

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45

50

55

60

MAC C35 CC CT SW

Ju

ice

co

nte

nt (%

)

Rootstocks

Fig.3 : Fruit juice content of Nadorcott mandarin grafted onto different rootstocks (20/02/2014)


ab ab aa a

20

25

30

35

40

45

50

55

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MAC C35 CC CT SW

Ju

ice

co

nte

nt (%

)

Rootstocks

Fig.2 : Fruit juice content of ‘Nadorcott’ mandarin grafted onto different rootstocks (13/02/2013)



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Total soluble solids

The fruits produced on the Citrus macrophylla gave a low TSS with statistically significant difference at p ≤ 0.05 % compared to those obtained on the other rootstocks. Poncirus and its hybrids are known to favor high quality of mandarin and orange production, while C. macrophylla is very productive but reduces fruit quality (Abouzar and Nafiseh, 2016).

c

a a

ba

0

2

4

6

8

10

12

14

MAC C35 CC CT SW

TS

S %

Rootstocks

Fig.4 : Soluble sugars content in fruit ‘Nadorcott’ mandarin grafted on different rootstocks (13/02/2013)


cb a b ab

0

2

4

6

8

10

12

14

16

MAC C35 CC CT SW

TS

S %

Rootstocks

Fig.5 : Soluble sugars content in fruit ‘Nadorcott’ mandarin grafted on different rootstocks (20/02/2014)


In the trial carried out by Tazima and al. (2013) to assess the performance of ‘Okitsu’ Satsuma mandarin grafted onto nine rootstocks in the northern region of the Paraná State, Brazil, in terms of plant growth, plant yield and fruit characteristics, the highest values for TSS were observed for fruits from trees on the trifoliate orange, ‘Volkamer’ lemon, and ‘Carrizo’ citrange rootstocks.

Acid content

Fruit produced on the Citrus macrophylla have low acidity compared to other rootstocks; this decrease in acidity was well marked in 2014. The lack of clear effect of rootstock on acid content of citrus is a common phenomenon recorded in similar studies (Al-Jaleel and Zekri, 2003).


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aa a a a

0,0

0,2

0,4

0,6

0,8

1,0

1,2

MAC C35 CC CT SW

Titra

ta

ble

a

cid

ity (%

)

Rootstocks

Fig.6 : Titratable acidity in fruit ‘Nadorcott’ mandarin grafted on different rootstocks (13/02/2013)


ba

aa

a

0,0

0,2

0,4

0,6

0,8

1,0

1,2

MAC C35 CC CT SW

Titra

ta

ble

a

cid

ity (%

)

Rootstocks

Fig.7 : Titratable acidity in fruit ‘Nadorcott’ mandarin grafted on different rootstocks (20/02/2014)


Maturity index

The fruits produced on the five rootstocks meet the standards of CEE-ONU FFV-14 adopted by the Autonomous Control, Marketing and Export Establishment (EACCE) of Morocco who requiring a maturity index (TSS / A ratio) equal to or greater than 7.5 (Fig. 8 and Fig. 9).

Within the 2013 season, Citrus macrophylla induced the lowest maturity index (11.3), while CC and C35 gave the highest indices which correspond successively to 13.1 and 13. In the other hand CT and SW induced to ‘Nadorcott’ mandarin intermediate indices, successively of 12.6 and 12.8. The low maturity index noted on MAC is due to the low TSS, following a low TSS / A ratio.


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In contrast, in 2014 the fruits harvested on MAC scored the highest maturity index (16.95) although remains statistically not significant compared to the other values recorded by the other rootstocks (Fig. 9). It is reported that the rootstock affects many characters related to fruit quality. Among these characters: juice content, skin color, soluble solids, acid concentrations and their ratio (Castle, 2010b) Larger fruit with thicker, rougher peel and lower concentrations of TSS and acid in the juice are generally associated with cultivars budded on fast-growing, vigorous rootstocks such as rough lemon, Volkamer lemon, Citrus macrophylla and Rangpur. However, these rootstocks impart high vigor to the scion and induce high yield. Cultivars on slower growing rootstocks like citranges and citrumelos produce fruit with smooth peel texture and good quality fruit with high TSS and acid content in the juice (Zekri, 2011). Fruit color

No significant differences were observed between rootstocks on fruit color parameters (Fig. 10). In addition of rootstock, fruit coloration is governed by several factors such as fruit maturity, tree nutrition, cultivation practices, water availability, and temperature. Fruit color also depends on climatic conditions and groundcover in the orchard (Ladanyia, 2010). In addition, Demirkeser and al. (2009) reported that the rootstocks did not affect the skin structure, rind color or ease of peeling for ‘Nova’ mandarin.

a aa

aa

a aa a a

a a a a a

a a a a a

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MAC C35 CC CT SWCo

lou

r p

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mete

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,L)

an

d C

CI

valu

es

Rootstocks


Fig.10: Effect of rootstocks on fruit color of "Nadorcott" mandarin (2015)

a

b

L

CCI

Coloration of typical mature fruit should be present in at least one third of the fruit surface for all mandarins commercialized (European norms and directions about citrus fruit quality standards adopted by EACCE of Morocco).


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The Citrus Color Index (CCI) is calculated by the formula proposed by Jimenez-Cuesta et al. (1982) below:

CCI = 1000 X a / L x b Citrus Color Index interpretation scale (Jimenez-Cuesta et al. 1982) For a CCI


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